1. Field of the Invention
The present invention relates to a method of aging a field emission device, and more particularly, to a method of aging a field emission device by which the problem of short circuits produced during the fabrication of the field emission device can be overcome, thus enabling normal operation of the field emission device.
2. Description of the Related Art
In general, electron emission devices may be categorized into devices using a hot cathode as an electron emitter or devices using a cold cathode as the electron emitter. As is well known, electron emission devices using a cold cathode may be classified into Field Emitter Array (FEA) devices, Surface Conduction Emitter (SCE) devices, Metal Insulator Metal (MIM) devices, Metal Insulator Semiconductor (MIS) devices, and Ballistic Electron Surface Emitting (BSE) devices.
FEA electron emission devices are known as field emission devices. A field emission device operates on the principle that when an electron emitter is formed of a material having a small work function or a large B function, electrons are easily emitted due to a tunneling effect caused by an electric field in a vacuum. The electron emitter may have a tip structure with pointed tips, which may be formed of molybdenum (Mo) or silicon (Si) or be formed of graphite or Diamond like Carbon (DLC). In recent years, field emission devices have been fabricated using nano-materials, such as nanotubes or nanowires, as the election emitter.
Field emission devices may be classified into diode field emission devices and triode field emission devices depending on the arrangement of their electrodes. Specifically, a diode field emission device includes a cathode having a top surface on which an electron emitter is disposed and an anode disposed opposite the cathode. In a diode field emission device, electrons are emitted due to a potential difference between the cathode and the anode. A triode field emission device includes the same cathode and anode as a diode field emission device and further includes a gate electrode disposed adjacent to the cathode to discharge electrons. A Field Emission Display (FED) using a field emission device includes a fluorescent material layer that is arranged on a surface of an anode, so that electrons emitted from an emitter may be accelerated and contact the fluorescent material layer to emit light.
A field emission device undergoes an aging process in order to secure stable performance after the field emission device is manufactured. An example of a conventional aging method is to raise a voltage supplied to an anode slowly or to supply a smaller-width pulse signal with a rise in voltage, as discussed in Korean Patent Publication No. 2004-90799. Also, a method of raising voltages of an anode, a gate electrode, and a cathode by degrees is discussed in Korean Patent Publication No. 2005-105409. In still another example, Korean Patent Publication No. 2006-20288 introduces a method in which a current is periodically measured, and when the current is smaller than a target current, the current is increased by feedback. However, these conventional methods do not provide a method of repairing a short circuit of a field emission device, which is detected in an initial stage of an aging process.
FIGS. 1A through 1C are photographic images of types of short circuits of a triode field emission device. The triode field emission device shown in FIGS. 1A through 1C employs an emitter formed of Carbon NanoTubes (CNTs).
The causes of the short circuits of the triode field emission devices shown in FIGS. 1A through 1C are as follows. First, referring to FIG. 1A, during formation of an emitter 5 of a triode field emission device, the emitter 5 may be misaligned with a central portion of an emitter hole 3 so that the emitter 5 comes very close to or into contact with a gate electrode 2. Second, referring to FIG. 1B, a portion of an emitter 5 extends like a fine thread (refer to 5A in FIG. 1B) and contacts a gate electrode 2. Third, referring to FIG. 1C, a gate electrode 2 is connected to a cathode 1 due to CNT emitters or an extraneous substance 6.
Therefore, when a conventional aging process is performed on a field emission device having a short-circuited portion, overcurrent flows into the short-circuited portion and a large electric arc may occur, with the result that the short-circuited portion may be permanently damaged.
FIG. 2 is a photographic image of an FED 10 that is permanently damaged after a conventional aging process. Referring to FIG. 2, when a normal driving voltage is supplied to an anode and a cathode after a conventional aging process is performed on the FED, electron beams are not emitted from permanently damaged portions. Thus, it can be confirmed that a plurality of horizontal lines from which electron beams are not emitted are formed. The horizontal lines appear after the FED performs a scan operation in a horizontal direction. In a steady mode, electrons collide with a fluorescent layer coated on an anode so that light is emitted. However, the horizontal lines where light cannot be emitted 11 since a voltage is not supplied to a permanently damaged scan line.